The Australian Transport Safety Bureau (ATSB) is Australia's national transport safety investigator. The ATSB's function is to improve safety and public confidence in the aviation, marine and rail modes of transport. The ATSB is Australia's prime agency for the independent investigation of civil aviation, rail and maritime accidents, incidents and safety deficiencies.

On the afternoon of 13 March 2003, the pilot of a Eurocopter
AS350-B2 helicopter, registered VH-PHB, was conducting a police
surveillance operation to the north and west of Bankstown, NSW at
4,000 ft. The pilot was operating on the Departures West radio
frequency. The area of operation for the helicopter was not clearly
defined and a clearance limit had not been applied. The Departures
West controller had passed radar identification details of the
helicopter to the Departures South controller as the helicopter was
operating in that controller's area of responsibility. The
Departures South controller was required to ensure that any
aircraft under their jurisdiction was separated from the observed
radar track of the helicopter. However, the helicopter was
maintained on the Departures West radio frequency. The Departures
West control position was subsequently subject to a
handover/takeover to a new controller.

A short time later, a Saab 340B (Saab), registered VH-KDQ,
departed Sydney Airport's runway 34 left (34L) at about 1805
Eastern Summer Time on climb to 3,000 ft into the Departures South
controller's area of responsibility. The Saab was followed, with
minimum radar separation, by a de Havilland DHC-8-314 (Dash 8),
registered VH-TQA. The Departures South controller was concerned
that the Dash 8 was faster than the Saab and consequently cleared
the Saab crew to climb to 5,000 ft at about 1807. About one minute
later, a short-term conflict alert (STCA) activated on the TAAATS
system and a breakdown in separation occurred between the Saab and
the helicopter.

The pilot of the helicopter was immediately instructed to turn
left and was given traffic information about the Saab by the
Departures West controller. After the pilot reported seeing the
Saab, he was instructed to maintain visual separation from it. The
Departures South controller, who also received the STCA, instructed
the crew of the Saab to turn left onto a southerly heading to move
it away from the helicopter's position. Recorded radar data
indicated that the minimum separation between the helicopter and
the Saab was 2.15 NM laterally and 700 ft vertically.

The investigation found that the Departures South controller had
been operating in that control position for 15-20 minutes before
the occurrence. As the Departures West controller had only recently
assumed responsibility for that position, it is possible that
neither controller realised the extent of the area of operation of
the helicopter. The Departures South controller was also distracted
by the close proximity between the departing Saab and Dash 8.

The occurrence aircraft, although operating in the same volume
of airspace, were operating on different control frequencies. The
controllers did not clearly enunciate which of them was responsible
for separation of the occurrence aircraft. As the area of operation
for the helicopter was not clearly defined, it was difficult for
the controllers to apply separation assurance.